<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>Title</title>
</head>
<body>
  <script>
    let obj={x:100}
    let obj2={y:200}
    Object.defineProperty(obj2,'x',{
        get(){
            return obj.x;
        },
        set(value) {
            obj.x=value
        }
    })
  </script>
</body>
</html>